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Research on the cognitive and emotional capacities of dogs is a "hot" area of study. At least weekly, it seems, we're learning something fascinating about how dogs sense their world, and these data are allowing us to understand not only how they interact with one another, but also with other nonhuman animals and ourselves.
Along these lines, a new study published in ScienceDirect by Natalia Albuquerque and her colleagues called "Mouth-licking by dogs as a response to emotional stimuli" shows that dogs read angry human faces, and mouth-lick when they do so. The entire research essay is available online. Here are few snippets to whet your appetite for more. (A summary of the above study called "Dogs mouth-lick to communicate with angry humans" nicely captures the essence of what these researchers discovered.)
Albuquerque and her colleagues studied how 17 adult family dogs responded to angry dog and human faces by simultaneously exposing dogs to grey-scale facial images of positive or negative faces of unfamiliar dogs or humans. They also paired sounds with the images.
For each dog, they calculated "the number of 'mouth-licks' displayed in a given condition divided by the total number of 'mouth-licks' displayed by that dog" and this measure IML. According to the researchers, this standardized metric "was calculated in each of the following conditions: (i) looking at negative face with a negative vocalization stimulus, (ii) looking at negative face with a positive vocalization, (iii) looking at positive face with negative vocalization, (iv) looking at positive face with positive vocalization, (v) looking at negative face with control sound, (vi) looking at positive face with control sound. If mouth-licking was displayed when the dog was looking away from the screens (right after it had been looking at the images) we referred to the most recent image that they had looked at before mouth-licking."
Overall, mouth-licking by dogs was restricted to human, not dog, visual stimuli representing anger, rather than auditory (vocal) stimuli, Based on their detailed analyses of the data, the researchers rightly concluded that dogs read us well and that dogs "have a functional understanding of emotional expressions." In other words, they read facial expressions of anger very well. In the researchers' own words, "The results of the current study add to our earlier findings that dogs can extract the emotional content of facial expressions of others (Albuquerque et al., 2016), by indicating that they can also respond to this information in a functional way."
Daniel Mills, a co-author on the paper, notes, "These results indicate that dogs may be using the visual display of mouth-licking to facilitate dog-human communication in particular."
Can dogs tell us we're angry when we don't know we are?
This research has a number of important potential scientific and practical aspects. Not only does it highlight much of what we seem to "know" intuitively about how dogs read us, but it also provides data that expand this knowledge.
There might also be a practical side to what these researchers learned: When I mentioned this study to someone who works in the business sector and who's very interested in animal cognition, they asked two interesting questions. First, do dogs have anger-detecting neurons, and if so, can dogs be used to diagnose anger issues when a person isn't aware of their feelings?
I couldn't answer these questions with any certainty. I assume there are some neurons at work that allow dogs to read anger in human faces, but perhaps they're not used specifically for this purpose. I also wonder if in some cases dogs could be used when a therapist is counseling someone who is out of touch with their feelings.
It's also possible that these data might help any of us when we're interacting with someone who's not expressing anger verbally, and we see a dog begin licking her or his mouth. Of course, there doesn't seem to be a strict 1:1 causal relationship between mouth licking and human anger, but who knows where this research might lead. I look forward to more research on how dogs read us and the possible practical aspects of what we learn. There still is so much to discover about our interactions with dogs and other animals.
